Blog 17

2 Wheel controlled car

I made this on the Raspbery Pi for the stepper motor and for 'electric wheels'.

Stepper motor version

Hardware I used on my Raspberry Pi:

• One RPi_UI board | (User Interface)
• Two 7FETs | (7FETs)
• Two Jumper cables M-F
• Two IDC cable 6 pin
• Two 28BYJ-48 Stepper Motor

Programming:

• Bash

3D printed wheels code

I made the wheels in OpenSCAD and let them be printed out on a 3d printer. The OpenSCAD code:

$fs=0.2; $fa=2;

module stepperas(d=5, l=25, t=3) 
{
  difference()
  {
    cylinder (r=d/2 , h=l);
translate ([t/2, -5, -1])   cube([10, 20, l+2]);
translate ([-t/2-10, -5, -1])  cube([10, 20, l+2]);

  }
} 

difference()
{
  union () {
    difference () {
      cylinder (r=60/2 ,h=12);
      translate ([0, 0, 1.5])
        cylinder (r=50/2, h=20);
    }
    cylinder (r=6,h=6);
  }  

  translate ([0, 0, -1]) 
    stepperas(5.2, 20, 3.2);
}

The full car just went to be a carton box, with everything attached to it with tieraps.

'Electric wheels' version

Hardware I used on my Raspberry Pi:

• One RPi_UI board | (User Interface)
• One Motor | (Motor)
• One Cable, 4 Pin (I2C), F-F
• Two electric wheels
• Soft cables ( To connect to the motor and the wheels )
• One dongle

I also used some tieraps to attach the wheels on a board.

Programming:

• Bash

Script:

#!/bin/bash

#Wheel A left forward
#Wheel B Right forward 

# X is forwards - Y is backwards
#Wheels at front
#20  A backwards
#21  A forwards
#22  A stop
#30  B backwards
#31  B forwards
#32  B stop

while true; do
  BUTTON=`bw_tool -I -D /dev/i2c-1 -a 94 -R 30:b`

  if [ $BUTTON  = "20" ]; then
  #Car going forwards
  bw_tool -I -D /dev/i2c-1 -a 90 -W 21:80:b
  bw_tool -I -D /dev/i2c-1 -a 90 -W 31:80:b
  fi

  if [ $BUTTON  = "10" ]; then 
  #Car going backwards
  bw_tool -I -D /dev/i2c-1 -a 90 -W 20:80:b
  bw_tool -I -D /dev/i2c-1 -a 90 -W 30:80:b
  fi

  if [ $BUTTON  = "08" ]; then 
  #Car going left
  bw_tool -I -D /dev/i2c-1 -a 90 -W 21:30:b
  bw_tool -I -D /dev/i2c-1 -a 90 -W 31:80:b
  fi

  if [ $BUTTON  = "04" ]; then 
  #Car going right
  bw_tool -I -D /dev/i2c-1 -a 90 -W 21:80:b
  bw_tool -I -D /dev/i2c-1 -a 90 -W 31:30:b
  fi 

  if [ $BUTTON  = "02" ]; then 
  #Car Stops 
  bw_tool -I -D /dev/i2c-1 -a 90 -W 22:80:b
  bw_tool -I -D /dev/i2c-1 -a 90 -W 32:80:b
  fi

  if [ $BUTTON  = "01" ]; then 
  exit
  fi

 sleep 1
done

Other movements:

#Spinning right
bw_tool -I -D /dev/i2c-1 -a 90 -W 20:80:b
bw_tool -I -D /dev/i2c-1 -a 90 -W 31:80:b

#Spinning left
bw_tool -I -D /dev/i2c-1 -a 90 -W 21:80:b
bw_tool -I -D /dev/i2c-1 -a 90 -W 30:80:b

I think the code pretty much explains itself with the extra info I have given it. I used the push buttons as example of how it could be used. All the protocols can bee found in Motor protocol.